Lupus nephritis (LN) with a membranoproliferative pattern is an uncommon but recognized renal manifestation of systemic lupus erythematosus (SLE). While autoimmune myelofibrosis (AMF) has been described in association with SLE, the coexistence of primary myelofibrosis (PMF) with this pattern of LN has not been previously documented. We report a 50-year-old man with JAK2-positive PMF, undifferentiated connective tissue disease (UCTD), and Stage 3b chronic kidney disease who developed nephrotic syndrome and worsening kidney function. Initial serologic evaluation revealed positive antinuclear antibody (ANA), low serum complement C3, and negative antidouble-stranded DNA (anti-dsDNA) antibodies. Kidney biopsy demonstrated a membranoproliferative pattern of injury with mesangial and subendothelial immune complex deposits staining for IgM and C1q. Subsequent testing revealed high-titer anticardiolipin IgM antibodies. The patient met the 2019 EULAR/ACR classification criteria for SLE. Induction therapy with high-dose prednisone and mycophenolate mofetil resulted in a partial remission, with stabilization of renal function on follow-up. To our knowledge, this is the first reported case of LN with a membranoproliferative pattern of injury in a patient with PMF. The case underscores the diagnostic value of kidney biopsy in uncovering occult systemic autoimmune disease in patients with myeloproliferative neoplasms (MPNs), particularly when the clinical and demographic profile is atypical for SLE.

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A 7-year-old neutered male Cocker Spaniel with unrestricted access to rural land presented for progressive lethargy, tachypnea, and cough. Thoracic radiographs showed an unstructured interstitial pattern. Fine-needle aspirate (FNA) lung cytology identified pyogranulomatous inflammation with intralesional mushroom spores. Acute hypersensitivity pneumonitis (HP) was suspected, and treatment was initiated with oxygen supplementation and an immunosuppressive dosage of corticosteroid. Thoracic computed tomography (CT) and bronchoalveolar lavage (BAL) were performed on day 6, month 2, and year 1 to track therapeutic response and assess architectural changes. Clinical signs guided prednisone tapering and discontinuation. One year later, thoracic CT and BAL confirmed re-exposure to mushroom spores with mild persistent inflammation and CT changes suggestive of mixed parenchymal and small airway disease despite absent clinical signs. This case report emphasizes the importance of rapid identification of pulmonary mushroom spores for prompt immunosuppressive treatment. Unlike prior reports of lycoperdonosis with acute, fulminating, and generally fatal outcomes, this dog developed chronic HP.

Mixed cryoglobulinemia is a small-vessel vasculitis mediated by cold-precipitable immune complexes, and chronic hepatitis C virus (HCV) infection is its most common cause. Cutaneous disease, classically palpable purpura of the lower limbs, is the most frequent manifestation but is readily mistaken for cellulitis or other dermatoses, delaying diagnosis. We describe a 61-year-old woman with chronic HCV, a long smoking history, and active cocaine use who experienced more than a year of recurrent, painful, pruritic erythematous - purpuric eruptions of the lower extremities that were repeatedly treated empirically as cellulitis without benefit. She also reported new easy bruising and skin fragility. Inflammatory markers were elevated, an extended antinuclear antibody panel was negative, and serum cryoglobulins were positive; immunofixation of the cryoprecipitate demonstrated type III (polyclonal) mixed cryoglobulinemia. Urinalysis showed hematuria with low-grade proteinuria, indicating renal involvement, and complement C4 was at the low end of normal. The findings established HCV-associated type III mixed cryoglobulinemic vasculitis. Cocaine history required consideration of levamisole-adulterated cocaine vasculopathy, an important mimic. She was started on corticosteroids with rheumatology co-management and HCV-directed direct-acting antiviral therapy as the cornerstone of treatment. Following completion of antiviral therapy and achievement of sustained virologic response, cutaneous vasculitis resolved, urinalysis normalized with no evidence of active glomerulonephritis, and the corticosteroid dose was successfully tapered. The patient remains on prednisone 5 mg daily with ongoing taper. This case underscores cryoglobulinemic vasculitis as a cause of recurrent, cellulitis-like, lower limb eruptions, and the primacy of antiviral cure in achieving vasculitis remission.

Warm autoimmune hemolytic anemia (wAIHA) is an uncommon but potentially life-threatening autoimmune disorder characterized by immunoglobulin G (IgG)-mediated destruction of erythrocytes. Secondary wAIHA frequently occurs in association with systemic autoimmune diseases, particularly systemic lupus erythematosus (SLE), while Sjögren syndrome represents a less common but recognized association. Fulminant presentations with profound anemia remain rare and require prompt diagnosis, aggressive immunosuppressive therapy, and multidisciplinary management. We present the case of a 25-year-old woman with a history of reported Sjögren syndrome, Hashimoto thyroiditis, and clinical and serologic features concerning for evolving SLE who developed rapidly progressive direct antiglobulin test (DAT)-positive wAIHA. Despite receiving five units of packed red blood cells (PRBCs) at an outside hospital, her hemoglobin continued to decline after transfer, reaching a nadir of 3.2 g/dL. Laboratory evaluation demonstrated marked hemolysis with reticulocytosis, elevated lactate dehydrogenase, indirect hyperbilirubinemia, undetectable haptoglobin, spherocytes on peripheral smear, and a DAT positive for both IgG and complement (C3). The hospital course was further complicated by thrombocytopenia and severe splenomegaly, raising concern for autoimmune overlap syndrome and possible Evans syndrome. She was successfully treated with pulse-dose intravenous methylprednisolone, intravenous immunoglobulin (IVIG), folic acid supplementation, and transfusion support. Rheumatologic evaluation revealed positive antinuclear antibody (ANA), anti-SSA, antiphospholipid, and anti-thyroid peroxidase antibodies, prompting initiation of hydroxychloroquine. Hemolysis resolved rapidly with normalization of bilirubin, recovery of platelet count, and sustained improvement in hemoglobin, allowing transition to an oral prednisone taper without requiring rituximab or splenectomy. This case highlights that wAIHA may represent the initial manifestation of evolving systemic autoimmune disease and should be considered in young patients presenting with profound hemolytic anemia. Early recognition, aggressive first-line immunosuppressive therapy, timely transfusion support, and multidisciplinary collaboration can be lifesaving and may achieve complete hematologic recovery without the need for second-line biologic therapy.

Takayasu arteritis (TAK) is a rare large-vessel vasculitis in children. A 14-year-old girl presented with intermittent fever, elevated inflammatory markers (C-reactive protein up to 117.63 mg/L and erythrocyte sedimentation rate of 93 mm/h), and computed tomography angiography demonstrating diffuse wall thickening of the aortic arch and its major branches. She had a previous diagnosis of ulcerative colitis; however, colonoscopy and biopsy revealed severe chronic active proctitis with glandular architectural irregularity and occasional cryptitis, but without crypt abscesses or granulomas, and the overall findings were insufficient to confirm ulcerative colitis or intestinal Behçet's disease. Behçet's disease was excluded because of the absence of oral or genital ulcers, ocular lesions, and skin manifestations. The patient met both the 2010 EULAR/PReS/PRINTO and 2022 ACR/EULAR classification criteria for TAK. Initial treatment with prednisone and adalimumab induced remission. A disease flare in June 2025 (C-reactive protein, 53.43 mg/L; erythrocyte sedimentation rate, 50 mm/h; and worsening carotid artery wall thickening) was controlled by increasing the prednisone dose and adding tocilizumab. At the 10-month follow-up, she remained asymptomatic, with stable vascular findings. This case highlights the importance of applying rigorous diagnostic criteria to avoid overdiagnosis of Behçet's disease in children with TAK and nonspecific intestinal inflammation.

Steroid-responsive encephalopathy associated with autoimmune thyroiditis (SREAT), also known as Hashimoto encephalopathy, is a rare immune-mediated neurological syndrome with an incidence of 2.1 per 100,000 and a 4:1 female predominance. Neurological manifestations are independent of thyroid status, occurring in 30-40% of euthyroid patients, and include cognitive impairment, confusion, seizures, and psychiatric symptoms. Diagnosis is challenging in the elderly, where symptoms overlap with dementia or delirium, with only 51 reported cases in patients aged ≥65 years. We describe a 70-year-old woman with autoimmune hypothyroidism and levothyroxine nonadherence who presented with progressive weakness, melena, dyspnea, and altered mental status complicated by obstructive uropathy, gastrointestinal bleeding, hypocalcemia, and severe hypothyroidism. Despite normalization of metabolic parameters and thyroid function, profound encephalopathy with fluctuating alertness, psychomotor slowing, memory impairment, psychosis, and a seizure-like episode persisted. Workup revealed elevated anti-thyroid antibodies, positive ANA, inflammatory CSF, diffuse EEG slowing, and low-titer GAD65 antibodies. High-dose prednisone led to dramatic improvement within 48 h, fulfilling adapted Graus criteria for definite SREAT. This case distinguishes SREAT from myxedema coma by the temporal dissociation between thyroid normalization and steroid response, emphasizes avoiding overinterpretation of low-titer GAD65 antibodies, and highlights CSF findings as supportive evidence. Early recognition is crucial in elderly patients with refractory encephalopathy and autoimmune thyroiditis.

Primary cutaneous diffuse large B-cell lymphoma, leg type (PCDLBCL-LT), is an aggressive subtype of primary cutaneous B-cell lymphoma that predominantly affects the lower extremities of elderly individuals. We report a rare case of a 79-year-old woman presenting with rapidly enlarging, erythematous-to-violaceous tumors and plaques on the face, chest, left upper arm, and upper back, an uncommon non-leg manifestation of PCDLBCL-LT, confirmed by histopathology and immunohistochemistry. The patient was successfully treated with six cycles of the rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) therapy, achieving complete remission with no relapse during 1.5 years of follow-up. This case emphasizes that PCDLBCL-LT can present in locations outside the legs, highlighting the need for early recognition and systemic therapy in atypical locations.